Effect of Exogenous Application of Plant Extracts in Antioxidant Activity, Total Phenols and Steviol glycosides Content of Stevia Plant Under Abiotic Stress Conditions

A field experiment was conducted in the fields of the College of Agricultural Engineering Sciences/University of Baghdad to study the effect of Shading and the foliar application of some plant extracts on the natural antioxidant’s activity, total phenols and steviol glycosides content in the Stevia plant. Stevia plant seedlings, which produced from tissue culture of the Spanish variety Spanti, were planted on 15 April 2021. The experiment was conducted using a randomized complete block design (RCBD) using a split-plot arrangement with three replicates. The results showed that S 2 (Shaded plants) had significant superiority in the total antioxidant activity by 11000.20 mg L -1 , total phenols by 9.947 mg L -1 , and G 2 (Liquorice root extract) excelled in total antioxidant activity with 12852.50 mg L -1 . M 1 (Moringa leaves extract) showed significant superiority in total phenols with 16135 mg L -1 . The (G 2 ) exhibited the highest overall antioxidant activity when interacting with shaded plants. Additionally, the (M 1 ) contributed to a significant increase in total phenols in shady Stevia plants. Therefore, Stevia plants in the S2 (shading) with spraying of Liquorice root extract at the concentration of 6% have a significant increase of total antioxidant activity and total phenols. The S 1 (open field plants) were significantly superior in the total stevioside content (%) to the shaded plants S2, at a rate of 7.08%. It also showed that the spraying of Licorice root extract at the open field G 2 was significantly superior to G 1 , M 1 , and M 2 , and the control M 0 G 0 treatments at the following rates: 3.67, 5.70, 12.96, and 30.19%.